1. Field of the Invention
The present invention relates generally to spindle motors for use in disk drives, and more particularly to a spindle motor having a spindle motor stator for increased head stack assembly access.
2. Description of the Prior Art
The typical hard disk drive includes a disk drive base, and a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to the disk drive base. The head disk assembly includes at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA) that includes at least one transducer head, typically several, for reading and writing data to and from the disk. The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached heads are moved relative to tracks disposed upon the disk.
The head stack assembly includes an actuator assembly, at least one head gimbal assembly, and a flex circuit cable assembly. A conventional “rotary” or “swing-type” actuator assembly typically comprises an actuator body that rotates on a pivot assembly between limited positions, a coil portion that extends from one side of the actuator body to interact with one or more permanent magnets to form a voice coil motor, and one or more actuator arms which that extend from an opposite side of the actuator body. A head gimbal assembly includes at least one transducer head, sometimes two, which is distally attached to each of the actuator arms. The actuator assembly includes the actuator body which has a bore and a pivot bearing cartridge engaged within the bore. The at least one head gimbal assembly and the flex circuit cable assembly are attached to the actuator assembly.
The spindle motor includes a hub that is rotatably attached to the disk drive base. The hub has an outer flange that supports one of the disks. Additional disks may be stacked and separated with spacers. The spindle motor further includes an annular magnet and a spindle motor stator. Where space efficiency is of vital concern, the magnet is typically attached about the lowermost portion of the hub below the flange. The magnet consists of a predetermined number of N and S poles that are disposed alternately circumferentially about the magnet. The spindle motor stator includes an outer rim that is attached to the disk drive base and a plurality of internally facing stator teeth. The stator teeth are equally spaced and extend from the stator rim. The spindle motor stator is sized to fit about the hub and in particular the magnet. Each stator tooth includes windings which selectively conduct current to create a magnetic field that interacts with the various poles of the magnet. Such interaction results in forces applied to the hub which tend to rotate the hub. In those disk drives capable of reading both sides of the disks, the head stack assembly includes an actuator arm which extends and pivots between the vertical region between the lowermost disk and the spindle motor stator. A magnetic shield is provided between the head stack assembly in such region over the stator teeth for protecting against magnetic flux interacting with the magnetic data on the disk and the head stack assembly.
A topic of concern is the desire to reduce the overall disk drive size. Such disk drives may have a variety of applications such as in hand held or portable electronic devices. The exterior size and shape of the disk drive is often referred to as a “form factor”. Reduction of such disk drive form factor has proven challenging. This is because the mere reduction of the size of the various disk drive components may result in such components being unable to conform to required specifications and standard form factors for such components, and may result in installation or assembly difficulties.
One particular area of focus is the reduction of the height of the disk drive. As mentioned above, a prior art arrangement includes a lower actuator arm that extends and pivots between the vertical region between the lowermost disk and the spindle motor stator. Such prior arrangement is contemplated to be a limited factor in the overall sizing of the disk drive height. Accordingly, there is a need in the art for an improved spindle motor configuration in comparison to the prior art.